This invention relates to clutches, and more particularly to a one-way clutch apparatus.
Clutches are used in a wide variety of applications to selectively couple power from an input member, such as a driving disk or plate, to a second independently rotatable member such as a driven plate or disk. In some applications, it is further desirable to incorporate a clutch which allows for rotational movement of the driving member in a second rotational direction in which no clutch engagement occurs, and therefore in which no rotation of the driven member occurs. Such clutches are commonly referred to as xe2x80x9cone-wayxe2x80x9d clutches. With a one-way clutch, when a driving member is rotated in a first direction, the clutch causes engagement of the driving member with an external driven member. When the driving member is rotated in a second rotational direction opposite to that of the first rotational direction, the clutch releases the driven member from engagement with the driving member. The driving member is then allowed to rotate (xe2x80x9cover-runxe2x80x9d) freely or to xe2x80x9cfree wheelxe2x80x9d relative to the driven member.
Previously designed one-way clutches typically include some form of xe2x80x9cstrutxe2x80x9d which is positioned in a notch formed in either the driving member or the driven member. The strut typically xe2x80x9cfloatsxe2x80x9d in the notch during operation. While this design has proven to be a success and to work satisfactorily in many applications, it would nevertheless be even more desirable to provide a one-way clutch having some form of strut-like member which is more positively supported, and which does not xe2x80x9cfloatxe2x80x9d with respect to its supporting plate, but rather which xe2x80x9crotatesxe2x80x9d between engaged and disengaged positions relative to its supporting plate. Such an apparatus would be even more stable at higher rmp applications such as those in connection with transmissions being used with aircraft engines.
Yet another area where even further improvements over previously designed one-way clutches would be desirable is in connection with providing a strut-like engaging element for a one-way clutch which is not as critically dependent upon a copious amount of lubricant, such as oil, for proper operation. With previously designed one way clutches it is critically important that the pockets in the plate within which the strut is disposed be very well lubricated. This lubrication requirement becomes more difficult to satisfy as the transmission or other apparatus within which the one-way clutch is disposed is oriented in different angles, such as when a vehicle or aircraft associated with the transmission incorporating the one-way clutch changes its attitude relative to the earth""s surface. In such instances there may be momentary lapses of lubrication to the notches wherein the struts are housed. These lapses, in some extreme instances, could adversely impact the wear of the one-way clutch.
Still another area where even further improvement over previously designed one-way clutches could be achieved is the design of the strut or xe2x80x9ckeyxe2x80x9d which engages with the driven member when the clutch is rotated in one direction and disengages to allow free-wheeling when the driving member is rotated in a second direction opposite to the first direction. In some clutch designs the key rests within a recess or relief of a driving member and has one end thereof biased outwardly by a biasing member such as a spring. Since the key is not physically pivotally secured to the member upon which it rests, the entire key is free to xe2x80x9cliftxe2x80x9d, sometimes to a relatively large degree, which in turn might cause undesirable wear in the driven member positioned closely adjacent the key. Such wear might occur if, for example, the back end of the key (i.e., the end opposite to that which engages the driven member) lifts significantly to contact a surface of the driven member when the driven member is being rotated in a free-wheeling direction. Accordingly, it would be preferable to include some surface on the driven member which limits the lifting of the back end of the key to a very small degree even when the driving member is being rotated in a free-wheeling direction.
Yet another area where it would be desirable to reduce the wear-and-tear of a key of a one-way clutch apparatus would be in the design of the arm portions of the strut. At present, when the key is disposed on a driving member, a relatively large degree of clearance between the key and the driven member is required so that the arm portions of the key do not interfere with a surface of the driven member when the key is engaging a notch of the driven member. Thus, if the driven member is designed such that portions of a surface thereof limit the travel of the back end of the key, then the shape of the key arms becomes extremely important in allowing the key to pivot fully and engage the driven member without interfering with a surface of the driven member as the key engages therewith.
Accordingly, it is a principal object of the present invention to provide a one-way clutch apparatus which is adapted to couple a driving member with a driven member when the driving member is moved in a first rotational direction, and to allow the driving member to be moved freely relative to the driven member when the driving member is moved in a second rotational direction.
It is yet another object of the present invention to provide a one-way clutch having an engaging element which does not xe2x80x9cfloatxe2x80x9d in a related supporting member but is instead more positively supported for rotational movement relative to its supporting member, and which therefore is more stable in higher rpm applications.
It is yet another object of the present invention to provide a one-way clutch apparatus which is more immune to undesirable operating characteristics caused by a temporary lack of lubricant to the areas adjacent its engaging element, to thereby permit the one-way clutch to be used in applications where a transmission within which it is operating can be operated in a variety of attitudes relative to the earth""s surface without fear of a momentary lack of lubricant to the one-way clutch adversely affecting the wear and tear on the one-way clutch.
It is still another object of the present invention to provide a one-way clutch apparatus which is adapted for use with concentrically disposed inner and outer annular ring members such as annular gears to allow one of the concentrically disposed gears to drive the other when rotated in a first direction and to allow the two concentrically disposed gears to be uncoupled from one another when the former gear is driven in an over-running direction.
It is yet another object of the present invention to provide a one-way clutch apparatus in which portions of a surface of a driven member are used to limit movement of a back end portion of a key or strut disposed on a driving member when the driving member is rotated in a free-wheeling direction relative to the driven member.
It is still another object of the present invention to provide a one-way clutch apparatus in which portion of the surfaces of a driven member are used to restrict movement of a back end of a strut or key disposed on a driving member, and where a pair of arm portions about which the strut or key pivots are shaped such that the arm portions do not interfere with the surface portions of the driven member when the strut is engaging the driven member. In this manner, an automatic degree of xe2x80x9cdampingxe2x80x9d would be provided to the key or strut by the close proximate relation of various surface portions of the driven member which would limit undesirable lifting or other movement of the back end of the key or strut while the driving member is rotated in a free-wheeling direction.
The above and other objects are provided by a one-way clutch apparatus in accordance with preferred embodiments of the present invention. The apparatus generally includes a carrier plate having a cut-out portion and an engaging element in the form of a key supported within the cut-out portion for pivotal or rotational movement about a central axis of the key. Biasing means is further included for biasing the key such that first and second ends of the key are continuously urged outwardly of the carrier plate.
In the preferred embodiment the carrier plate is used in connection with a driving member having a key engaging portion formed in a surface thereof which faces the carrier plate, and with a driven member having a key engaging portion in a surface thereof which also faces the carrier plate. Accordingly, the carrier plate is disposed generally parallel between the driving and driven members. The key engaging portions of each of the driven and driving members are further disposed the same distance away from the axis of rotation of each of the members, and further the same distance from the axis of rotation as the key is disposed from the axis of rotation of the carrier plate. Accordingly, at some time during rotation of the driving member the key engaging portion therein will move directly over the key of the carrier plate. Since the carrier plate, driving member and driven member each rotate about a common axis, as the key in the carrier plate rotates it will at some time position itself over the key engaging portion of the driven member.
When the driving member is rotated in a first rotational direction, at some point during rotational movement thereof the key engaging portion moves directly over the key in the carrier plate. A first end portion of the key is urged into engagement with the key engaging portion in the driving member by the force of the biasing means, which in the preferred embodiment is in the form of a coil spring operably associated with the key. Engagement of the first end portion of the key in the key engaging portion of the driving member causes the carrier plate to begin moving rotationally with the driving member in the first rotational direction. As the key (and carrier plate) is moved rotationally to a position over the key engaging portion of the driven member the biasing force of the spring causes further rotational movement of the key itself such that a second end portion of the key engages or xe2x80x9cdrops intoxe2x80x9d engagement with the key engaging portion in the driven member. The driving member, carrier plate and driven member then all rotate in the first rotational direction with the key positively coupling the driving action of the driving member to the driven member.
When the driving member is moved in a second rotational direction opposite to that of the first rotational direction, the first end portion of the key will be urged rotationally out of engagement with the key engaging portion of the driving member. The driving member is then allowed to over-run (i.e., rotate freely) in the second rotational direction without driving engagement with the key, and therefore without engagement with the driven member. Thus, the driving member can xe2x80x9cfree wheelxe2x80x9d in the second rotational direction while the carrier plate and driven member remain stationary, or relatively stationary.
In an alternative preferred embodiment of the present invention the carrier plate is in the form of a carrier ring which is interposed concentrically between an inner annular ring and an outer annular ring. The carrier ring includes at least one cut-out portion within which a key is disposed for pivotal movement therein. Each of the inner and outer rings include at least one notched portion therein which is adapted to engage one or the other of the ends of the key.
When the outer ring, for example, is rotating in an over-running direction the key does not engage with the notch therein. Accordingly, rotation of the outer ring and the over-running direction does not impart any driving action to either the carrier ring or the inner ring. However, when the outer ring, for example, is rotated in the rotational direction opposite to that of the over-running direction, the key in the carrier is caused to engage the notch in the outer ring. As this occurs the carrier ring is driven rotationally concurrently with the outer ring for at least a short distance before engaging the notch in the inner ring. At this point the key transmits the full driving force of the outer ring to the inner ring thus causing the inner ring to rotate concurrently with the outer ring. It will be appreciated that the inner ring could just as easily be used as the driving ring in the outer ring as the driven ring. The principles of operation of the present invention are not dependent upon which of the inner or outer rings are used at the driving or driven ring.
The alternative embodiment just described above thus allows two concentrically disposed ring members such as annular gears to be driven together when one or the other is driven in one direction, and to be drivingly uncoupled when one or the other is rotated in the opposite rotational direction.
In the alternative embodiment described above the key may be spring biased such that its outermost ends extend slightly outwardly of the inner and outer surfaces of the carrier ring. Alternatively, the key may be formed such that its axis of pivotal movement is off center towards one of the outermost ends. This causes one of the outermost ends to be urged outwardly by a centrifugal force as the carrier ring rotates in one direction, and allows gravity to urge one of the ends outwardly of the carrier ring when the carrier ring is substantially stationary. Thus, the need for some independent biasing means such as a spring is obviated.
In yet another alternative preferred embodiment of the present invention a one-way clutch apparatus is disclosed in which portions of a surface of the driven member are formed so as to overlap portions of the pivot arms of a key or strut which is disposed on a surface of a driving member. The portions of the surface of the driven member which overlap portions of the arms of the key or strut positively limit the degree of movement of a back end portion of the key, such that the back end portion cannot rise significantly while the driving member is rotated in a free-wheeling direction.
To allow the above-described close placement of portions of the surface of the driven member relative to the arms of the key, the arms of the key are formed with ramp portions thereon to provide a degree of relief to the arm portions. This degree of relief enables a front end portion of the key to be urged outwardly by a biasing member, such as a spring, and to engage a recess in the driven member when the driving member is rotated in a driving direction (i.e., a direction wherein the key will engage the driven member and drive the driven member rotatably therewith). The ramp portions formed on the arms of the key provide the needed clearance between the arm portions and the portions of the surface of the driven member which would otherwise interfere with the movement of the key or enough for the ramp portions. The ramp portions formed on the arms of the key thus allow the key to be rotated a sufficient degree to engage a driven member without interfering with one or more surface portions of the driven member disposed closely adjacent the driving member, which limits the movement of the back end portion of the key. In this manner, the key is xe2x80x9cdampedxe2x80x9d by the closely positioned surface portions of the driven member. This enables the key to operate in a clutch being driven at a very high rpm, such as 5000 rpm or above. This arrangement further provides a means by which undesirable movement of the key can be xe2x80x9cdampedxe2x80x9d without completely flooding the areas adjacent the key with a lubricating fluid. Thus, the clutch apparatus is even less dependent upon a copious and continuous supply of lubrication to the key and the surface areas which it engages during driving operation.
Other objects, advantages and features of the present invention will become apparent to one skilled in the art upon reading the following description and dependent claims, taken in conjunction with the following drawings.